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Biomedical subjects

W F Malone

Publications and source records attributed to W F Malone.

At least 37 records · Page 2Linked to original sources
PubMed1991

Study of postnatal effects of chemopreventive agents on offspring of ethylnitrosourea-induced transplacental carcinogenesis in rats. I. Influence of retinol acetate, alpha-tocopherol acetate, thiamine chloride, sodium selenite, and alpha-difluoromethylornithine.

We studied the influence of the vitamins retinol acetate, alpha-tocopherol acetate and thiamine chloride; the antioxidant sodium selenite and an inhibitor of polyamine biosynthesis, alpha-difluoromethylornithine, on the offspring of transplacental carcinogenesis by ethylnitrosourea in rats. Ethylnitrosourea was given to pregnant rats as a single i.v. injection, at a dose of 75 mg/kg body wt. or 5.5 mg/kg body wt., on the 21st day after conception. Retinol, tocopherol or thiamine was added to the diet, and selenite and alpha-difluoromethylornithine to drinking water of the offspring throughout their postnatal life at moderate doses. In control groups, ethylnitrosourea induced tumors of brain, spinal cord, peripheral nervous system and kidneys in the offspring. alpha-Difluoromethylornithine exerted a slight inhibitory effect; this agent decreased the total tumor multiplicity and the multiplicity of peripheral nervous system tumors and also prolonged survival time. Retinol, tocopherol, thiamine and selenite did not influence the development of the transplacentally-induced tumors.

Animals↗
PubMed1991

Shear bond strength of two resin adhesives for acid-etched metal prostheses.

This study compared the shear bond strength of Panavia EX and Comspan Opaque adhesive resins with electrolytically etched or sandblasted Rexillium III or Litecast B metals bonded to extracted teeth. An analysis of variance revealed that there is no difference in bonding strength among etched or sandblasted Rexillium III metal with either Panavia EX or Comspan Opaque resins. With Litecast B metal, sandblasting produced a greater bond strength than etching with Panavia Ex resin (38.19 MPa sandblasted; 30.53 MPa etched). Conversely, Comspan Opaque resin had a value of 30.10 MPa etched and 15.40 MPa sandblasted. The etched Rexillium III and Panavia EX resins recorded a greater bond strength (38.38 MPa) than Comspan Opaque resin (27.83 MPa) or sandblasted Rexillium III metal (Rexillium III 34.74 MPa; Comspan Opaque 20.39 MPa) and Litecast B metal (Panavia EX 38.19 MPa; Comspan Opaque 15.40 MPa). Eighty percent of the failures occurred at the cement-metal interface with both cements.

Acid Etching, Dental↗
PubMed1991

Studies evaluating antioxidants and beta-carotene as chemopreventives.

Cancer chemoprevention research takes leads from epidemiologic and laboratory research and develops them through in vitro and in vivo preclinical research and initial human studies into randomized controlled clinical trials. At present, the chemoprevention program is sponsoring 21 human efficacy studies. These trials are testing the potential of agents (beta-carotene, folic acid, 13-cis retinoic acid, 4-hydroxyphenyl retinamide, vitamins C and E, and minerals) as inhibitors of a variety of cancers in humans (colon, lung, esophagus, cervix, bladder, and skin). Endpoints in these studies include overall incidence of cancer, incidence of specific cancers, rate of regression or progression of preneoplastic changes, and changes in cellular or biochemical parameters. Study participants include volunteers from the general population; populations at high risk for cancer because of occupation, lifestyle, or place of residence; persons with previously treated cancers; and persons with preneoplastic lesions. Study designs include single agent randomization, combination of agents and complete factorial designs.

Animals↗
PubMed1990

Concepts in cancer chemoprevention research.

Cancer prevention through the use of chemical intervention regimens (chemoprevention) is an emerging field with broad potential for impacting on cancer incidence rates in defined high-risk groups and the general population. Information from cancer epidemiologic studies coupled with that from basic research on cancer biology have combined to reveal several categories of agents with potential for clinical application, including natural and synthetic tumor suppressive retinoids and antioxidants. Chemopreventive agents may inhibit the development of cancer by limiting exposure to initiators or promoters through stimulation of inactivation or excretion mechanisms. Biological consequences of exposure to carcinogens may also be interfered with, e.g., by inhibiting the activation of proto-oncogenes or by antagonizing the effects of oncogene expression. Hundreds of compounds with chemopreventive efficacy in vitro have been isolated from foods and plant products. The testing and development of candidate chemopreventives proceeds through a series of preclinical efficacy screens, followed by controlled clinical trials.

Animals↗
PubMed1989

Chemoprevention and modern cancer prevention.

Chemoprevention is a new area of research emphasis in cancer control. The rationale is based on the accumulation of laboratory and epidemiological data indicating that various agents may halt or reverse cancer progression in animals and may reduce risks in humans. For planning purposes, research leads are submitted to a strategic system of staging with defined criteria and decision points. A research lead that enters an intervention stage must evolve through a series of phases of testing and evaluation. Human intervention clinical trials have begun to test the hypothesis that certain agents can lower cancer incidence.

Animals↗
PubMed1989

Tissue management with dental impression materials.

The coordination of perceptive tissue management, diligent tooth preparation and prudent selection of the impression material for specific clinical conditions ensures the success of cast and ceramic restorations. The introduction of a knitted cord (Ultrapak with Astringedent) has alleviated the arduous aspects of tissue displacement and the new impression materials have displayed exceptional accuracy but healthy tissue is fundamental.

Crowns↗
PubMed1988

Fluoride release from glass ionomers used as luting agents.

Four glass-ionomer cements were examined for solubility by measuring the fluoride release from a simulated dental restoration. From this study it may be concluded: 1. Glass-ionomer cements as luting agents for dental prostheses release significant quantities of fluoride. 2. Commercially available cements vary in the amounts of fluoride released. 3. The cements with lower powder-to-liquid ratios demonstrated greater fluoride release. 4. The significant release of fluoride indicated that glass-ionomer cements could be effective in reducing caries.

Cementation↗
PubMed1987

Chemoprevention of bladder cancer.

There is a growing body of basic science and epidemiologic evidence to support a research thrust to determine whether several natural or synthetic agents, given alone or together, can lower cancer incidence. Candidate agents include analogs of vitamin A and the vitamin A precursor, beta-carotene, vitamins C and E, and the trace metal selenium. Other agents now being studied in the laboratory include phenolic antioxidants, protease inhibitors, prostaglandin synthesis inhibitors, and indoles. Research in chemoprevention involves identifying and characterizing agents with reported activity, efficacy and toxicologic testing to select the most promising agents, and clinical trials to test those with the most potential in humans. Activities are underway in all the above areas, including 24 clinical trials, to evaluate selected compounds in preventing cancer at various cancer sites. Included are studies of individuals at high risk, individuals with precancerous lesions and individuals free of cancer but at risk to second cancers. A number of agents have shown activity in reducing bladder cancer incidence in animal models. The potential applicability of these agents for studies in human cancer risk reduction intervention studies is discussed. Cancer induction is postulated to be a multistage process involving initiation and promotion. Progress in cancer prevention may result from not only reducing exposures to initiators, but also suppressing promotional activity in initiated cells. Newly developed research technologies including cellular, animal, and epidemiologic procedures are being used for identifying, refining, and testing cancer prevention strategies.

Animals↗
PubMed1986

Clinical trials in cancer prevention.

Research in cancer prevention can be divided into laboratory research, epidemiologic research, and clinical trials. When results from laboratory and/or epidemiologic research support the possibility of clinical cancer prevention, these leads should be subjected to study in clinical trials. If clinical trials produce positive results, wide application of these results to the relevant segments of the general population should then be emphasized. Why are clinical trials needed in cancer prevention? There are several considerations: epidemiologic studies may lack specificity, that is, the ability to reach conclusions that apply to only one specific factor; the predictive value of animal models based on laboratory studies is not entirely known; clinical trials quantitate the level of participant acceptance of the intervention; and clinical trials address the issues of risk/benefit ratios. Over the last 3 years, the National Cancer Institute has supported the development of a program of clinical trials in cancer prevention. The aim of these studies includes the reversal of precursor lesions, prevention of progression from a precursor state to overt malignancy, reduction in the incidence of malignancy, reduction in cancer mortality, and reduction in overall mortality. Interventions under study include a diet with less than 20% of calories from fat, and the administration of single agents or combinations of agents, including beta carotene, vitamin A, 13-cis-retinoic acid, vitamins C, E, and B12, and folacin.

Clinical Trials as Topic↗
PubMed1986

The National Cancer Institute's Cancer Prevention Research Program.

The National Cancer Institute (NCI) develops and supports a broad range of research relevant to screening for preneoplastic events and biological effects of carcinogen exposure. In cancer screening and detection, NCI supports studies on development of new methods for detecting cancer and/or preneoplastic states, systematic testing of new screening methods, and wider application of established methods. Recently, NCI developed clinical trials in chemoprevention and dietary intervention. These studies focus on populations identified by markers of exposure or markers of increased risk, and have as their end point reduction in cancer incidence.

Humans↗